It has been 20 days since Washington Nationals outfielder Bryce Harper injured his left knee by running into the outfield wall at Dodger Stadium, and lingering effects led the team to place the 20-year-old on the disabled list Saturday.

Harper had sat out the past five games with bursitis, and the Nationals had hoped the swelling would subside. But he still had pain after taking batting practice Friday in Atlanta, where Washington is in the middle of an important three-game series with the Braves. Washington was 28-27 through Friday, 4 1/2 games behind the Braves in the National League East.

Harper will be eligible to come off of the disabled list June 11, with the move retroactive to May 26. Had he began his recovery sooner after the May 13 injury instead of attempting to keep playing, his return might have come earlier for Washington.

"If we felt he'd be back in three to five days, we couldn't have DL'ed him," manager Davey Johnson told reporters before Saturday's game.

On top of that, ace right-hander Stephen Strasburg flew back to Washington after exiting his Friday start after two innings because of a strained right oblique, revealed by an MRI on Saturday. Johnson said the team wants to see how Strasburg's condition improves over the next two days before making any decisions regarding his status. His next scheduled start is June 8.

Right fielder Jayson Werth, who hasn't played since May 2 because of a hamstring injury, was expected to return to the lineup next week.

On June 25, 2013, Bryce Harper plays for the Potomac Nationals in a rehab assignment. rounds second base in the third inning against the Myrtle Beach Pelicans at Pfitzner Stadium. Harper plays for Potomac in a rehab assignment. Joy R. Absalon, USA TODAY Sports

Bryce Harper warms up in the on deck circle during a rough loss against the Giants. After the game, Nationals closer Rafael Soriano critizes Harper for being out of position in right field. Ed Szczepanski, USA TODAY Sports

When Harper registered at least one RBI in a game, Washington went 30-8 (.789). When he scored a run, the Nationals played .743 ball (55-19). And when the left-handed hitting rookie homered, the Nationals finished 15-5 (.750). Brad Mills, USA TODAY Sports

Harper won the NL Rookie of the Month award in both May (.271, 13 extra-base hits, four home runs, .860 OPS) and September (.330, seven doubles, three triples, seven home runs, 14 RBI, 1.049 OPS). Evan Habeeb, USA TODAY Sports

Harper is the first DC-based player to win a rookie of the year award since outfielders Albie Pearson and Bob Allison claimed consecutive American League awards in 1958 and '59, respectively. Matt Slocum, AP